The aim of this study was to compare 99mTc-bicisate with 133Xe inhalation in regional CBF (rCBF) imaging. Five healthy volunteers and five patients were imaged with both techniques. Regional standardized values (SVs) of 99mTc-bicisate, uptake indexes (UIs), and asymmetry indexes (AIs) were compared quantitatively with, respectively, rCBF, flow indexes (FIs), and AIs. Areas with highest rCBF (sylvian and thalamic areas) appeared to be underestimated with 99mTc-bicisate, but significant correlations were found between SV and rCBF (n = 140, r = 0.468, p < 0.01) and for the 10 subjects between UI and FI and between AIs (p < 0.0001). There are therefore distinct regional differences in the cerebral distinction of 99mTc-bicisate and CBF, particularly in the thalamus and the temporal cortex. It is probable but not yet proved that an underestimation of high flow rates occurs with bicisate.